The present invention relates to systems for controlling the air pressure within an enclosure, such as an aircraft cabin. This invention, which controls the air pressure in such an enclosure to ensure passenger comfort and safety, includes digital systems for monitoring and testing system components to provide fail-safe operation.
Control of aircraft cabin air pressure is important for both the comfort of passengers and crew and safe aircraft operation. Many present-day aircraft fly at elevations of 35,000 feet or higher; and the cabin air pressure control system for such aircraft must provide adequate oxygen to occupants of the aircraft without permitting sudden changes in the cabin air pressure, to which the human ear is sensitive, and without developing a dangerously high pressure differential between the cabin air pressure and the ambient pressure to prevent overstressing of the structural components of the aircraft.
Some prior art cabin pressurization systems have the disadvantage that a member of the flight crew must periodically compare the rate of change of the cabin altimeter reading, which is related to the cabin air pressure, to the rate of change of the aircraft altimeter to ascertain whether the system is functioning properly. Many prior art cabin pressurization systems determine the cabin air pressure based upon a setting of the take-off altitude, the cruise altitude and the landing field altitude above sea level; but, under certain atmospheric conditions, such systems permit rapid changes in aircraft cabin pressure, which often causes discomfort to the passengers and crew due to the sensitivity of the human ear to changes in air pressure.
Prior art aircraft pressurization systems have the added deficiency of failing to provide built-in monitoring and testing of subsystems and flight data which designers of modern aircraft require to ensure reliable operation and to minimize risks in the event of system failure.
Accordingly, there is a need in the art for an aircraft cabin pressurization system which requires minimal attention from the crew, maintains constant pressure under adverse atmospheric conditions and sudden, small changes in aircraft altitude, and which includes means for monitoring and testing critical components within the system to ensure safe, reliable operation.